In oil field operations, pressure sensing tools are utilized in downhole operation for measuring pressure in a well bore. These tools typically involve a pressure tight housing in which pressure in the borehole operates a capacitance measuring system in the tool for developing signals representative of downhole pressure. Prior art systems are set forth and explained in my prior U.S. Pat. No. 4,091,683, issued May 30, 1978.
The problem which the present invention addresses is the fact that FET devices are temperature responsive in that increasing the temperature of operation causes current leakage which can either causes inaccuracy in the measurements at downhole temperatures or failure of the systems to operate.